Department of Geological Engineering

This study investigates basin-type granitoid samples from the north-eastern margin of the Kumasi Basin in Ghana to establish their source and geodynamic setting. Petrographic analysis, TAS and A/NK-A/CNK plots classify the granitoids as metaluminous quartz diorite, metaluminous granodiorite, and peraluminous monzogranite; and exhibiting I-type signatures. These rocks are formed by magma differentiation and/or partial melting at various stages. Distribution patterns of incompatible elements and the positive Eu/Eu* anomalies of 1.15 and 1.47 exhibited by quartz diorite and granodiorite, respectively, the values suggest the rocks crystallized from melts formed in a water-saturated environment. The negative Eu/Eu* anomaly exhibited by monzogranite indicate fractionation of plagioclase in the final stages of the magma evolution. The water-rich environment is probably due to dewatering of the basin’s foreland volcaniclastic sediments during regional subsidence, burial and metamorphism. K2...

This paper uses risk assessment of socio-economic and environmental indicators to develop criteria for apportionment (AP) of funds to communities impacted by mining activities within a Forest Reserve environment in Ghana. A t-test statistic of assessment data shows that factors such as; cost of living, health conditions, air pollution, water contamination, land degradation and distance (D km) are significant. Ratings of the factors using a 1-5 intensity scale to determine risk values (RV) for communities indicate that RV of 25 requires no remediation, while (25-RV) is remediation factor. A long-term AP criterion using the ranked risk (RR) values is defined by the equation APRR%=7.45-0.233(RR) with R2 of 0.961. Based on this criterion, communities D and S which are located at 1.5 and 16.1km from the mining focus have APRR values of 7.23% and 2.26%, respectively. APRR% in relation to distance is defined by the equation APRR%=7.22-0.281(D) with R2 of 0.647. RR-dependent distance equati...

This study investigated the issue of tailings dams as a potential source of trace elements contamination in soils at the Obuasi gold mine in Ghana. Soil samples taken from depths of up to 12 cm and within a radius of 400 m from the tailings dams (active and decommissioned), were analysed for As, Cu, Pb and Zn using atomic absorption

ABSTRACT This study assessed the geochemical impact of mine tailings reclamation on the quality of soils from the AngloGold Concession, Obuasi, Ghana. Soil samples from mine tailings reclamation sites were evaluated for the concentrations of plant nutrients and trace metals. Contaminations of trace metals, using geochemical pollution indices were used to assess possible effects on agriculture and livelihoods. The average pH ranges from 7.6 to 8.4 at the ex-tailing sites whiles the control site is 6.0. Organic carbon and nitrogen levels at the ex-tailings site are low due to topsoil loss. Average available P and K levels were low or very low; i.e., <20 and <40 mg/kg, respectively at both ex-tailing and control sites. Average EC values as well as individual values of all the soils were less than 2 dS/m, while average ESP and individual soil values were less than 15%, indicating that the soils are non saline. Average ECEC levels, contributed by Ca and Mg, are medium at the ex-tailing sites but low at the control sites. The concentrations of arsenic (As), copper (Cu), lead (Pb) and zinc (Zn) were compared to their respective background concentrations to calculate their contamination factors and geo-accumulation indices at all the examined areas. Average concentration values for As are consistently high; presenting the highest value of 426.67 mg/kg at Area 3 and the least of 72.03 mg/kg at the control site, above the Netherlands soil/sediment intervention guideline value of 55 mg/kg for remediation. Furthermore, estimates from the geochemical evaluations indicated that As contamination was very high and therefore poses a threat to agricultural land use as well as general environmental quality.

ABSTRACT This study assessed arsenic (As) contamination and the characteristics of secondary minerals in mine drainage using integrated acid-base accounting (ABA) and toxicity characterisation leaching procedure (TCLP), aqueous and solid-phase media monitoring, as well as a textural and mineralogical analysis of tailings material at the Obuasi mine in Ghana. The neutralisation potential and maximum potential acidity from an ABA test; As and pH in TCLP leachate and mine drainage, particle size, trace and major elements in tailings, were analyzed using the relevant methodologies. The ABA results which indicated a high tendency for acid generation were interpreted using a four data point model developed for the purpose. The model allows an additional 40 kg CaCO3/ton amendment value to take care of any delayed acidification. Arsenic leaching simulations are described by the equation: [As] \(= {\text{A }}\left( {\frac{\text{NP}}{\text{MPA}}} \right)^{2} - \;{\text{B}}\left( {\frac{\text{NP}}{\text{MPA}}} \right)\; + \;{\text{C}}\) . With the y-axis set to zero, pH simulation equations are defined by pH = K \(\left( {\frac{\text{NP}}{\text{MPA}}} \right)\) , where the K and pH values ranging from 82 to 100 and 4.1 to 9.0 respectively, represent limits within which natural attenuation of As in drainage can be sustained. Expressing the pH equation above in the form, pH = (ln |R2| − lnK), the simulation equations defined the range 2.2-4.6 which conformed to pH range for which secondary minerals such as jarosite, schwertmannite and ferrihydrite, could occur as buffering agents in mine drainage. Also, molar value plot for Fe2O3 against Al2O3 indicate the precipitation of goethite and alunite into tailings, while increased fines and As enrichment in older tailings confirmed As attenuation. Such information is relevant for front-end planning for As impact remediation in mine drainage.

This paper evaluates some geochemical properties of trace metals in peri-urban drainage and bioaccumulation in cassava, plantain, lettuce and sugarcane in the Kumasi metropolis in Ghana, West Africa. The aim is to establish water quality and food safety. Water, sediment and the food crops were sampled along the profiles of Wiwi and Subin rivers for analysis. T-test statistic shows that pH, HCO3, Cl, Cu, As, Pb and Ni are significant in water and sediment. Mean concentrations of Cu, As, Pb and Ni in water and sediment are (0.01mg/l; 3.2mg/kg), (3.08mg/l; 4.9mg/kg), (0.034mg/l; 8.7mg/kg) and (0.021mg/l; 6.1mg/kg), respectively. In water, As, Pb and Ni concentrations are above primary maximum contamination limits of 0.05 mg/l, 0.015 mg/l and 0.020mg/l with metal ratios of 61.54, 2.27 and 1.05, respectively. In sediment, As concentration is above the continental crustal background value of 1.8mg/kg with a metal ratio of 2.72. From geochemical process models: (1) As and Ni adsorbs into s...

This study presents gold mineralisation and pathfinder elements characteristics in five surficial regolith profiles, with the aim of enhancing exploration strategies in the northeastern Bole-Nangodi Gold Belt in Ghana. Samples were collected from mature soils and bedrocks in exploration pits and prepared for chemical and soil particle size analysis. 13 major elements , mineral forms and fifty-one trace elements were analysed using XRF, XRD and ICP-MS devices, respectively. SiO 2 , Fe 2 O 3-MnO and Al 2 O 3 are elevated in the A, B and C horizons, respectively, while Na 2 O-K 2 O-MgO-CaO-P 2 O 5 systems dominate the bedrocks. Gold pathfinder element suites of As-Mo-Ag-Sn-Sb-Te-W-Hg-Bi are above Primitive Mantle values by a factor of > 5, while the mean chemical index of alteration (CIA) values are above 80%. Profiles contain > 70% quartz with stable mineral concentrations of 53, 18 and 29% in the A, B and C, horizons, respectively. The B horizon is the most altered horizon based on CIA, loss on ignition and Fe/Al ratios; the horizon accounts for 52% of the material and 76% of elements in the > 2 mm particle size. Mass balance and principal component analysis shows that Au exploration targets and the associated pathfinder element suites are the following: (1) horizon A with Sr-CaGe -Sn-Th in the amphibolite and biotite gneiss profiles (2) horizons A and B with S-K-Zr-Tl-Ge in the volcaniclastic and (3) the bedrocks with Cu-Pb-Sb-Ag-Mo and Mn-Cr-Ba-V-Ce-Bi-Fe-Co-Sb-As-Se of the metavolcanic and phyllite profiles, respectively. The regolith models summarise the mineralogical and structural framework of the profiles and may largely influence exploration designs.

This study assesses environmental receptors impacted by alluvial gold mining at Kibi Goldfields Limited in the Eastern region of Ghana to establish trace metals contamination risk. Specific objectives are to determine concentrations of (1) As, Cr, Ni and Pb in soils, drainage and food crops, using X-ray fluorescence, (2) Cl- in drainage using standard methods. Mean concentrations of As, Cr and Ni in soils are higher at impacted sites than control sites; while Pb and As concentrations in drainage exceeds the maximum contamination guideline values in drinking water. Using Cl- as a conservative tracer, As and Pb are adsorbing from water, while Cr and Ni are desorbing into water. In the food crops, bioaccumulation factors of As and Ni are profound at the impacted site than control sites; Except Cr in cocoyam at impacted sites, translocation factors are negligible in the food crops. Cr bioaccumulates in in cocoyam and plantain at the control site, while Ni bioaccumulates in only plantain...